Making a copy in Terminal with rsync
where are the nearly 100GB coming from ?
Fragmentation.
There are over 350,000 files in a MacOS image alone, and unless you pack everything really tightly, making a copy will be larger than the original because the unused leftover fragments of blocks are not a good place to START writing a NEW file. Over time, as you read and re-write files on that volume, the size may contract slightly as things get optimized with use.
Not a Bug. Not really a surprise.
Very soon you would have needed a bigger drive regardless. But drives are cheap, and backup drives don't have to be especially FAST. It sure is a great time to be alive.
My back up size is larger than the source
